A cross polarization could be indispensable in certain applications when scanning and digitizing highly reflective materials or when certain applications couldn’t afford following the recommended imaging geometry 0<sup>0</sup>/45<sup>0</sup> | 45<sup>o</sup>/0<sup>o</sup> for some technical reasons. However, that puts very much color fidelity in question, to which extent a cross polarization may impact the source illuminant in the first place that is consequently impacting the color appearance during the imaging and the color correction procedures. In this research we show how certain cross polarization setups are adding a chroma tint to the light source, D50 in this study, causing by that undesirable color shift of the color of the light source. Consequently, a shift in its color correlated temperature moving, in worst case scenario, from ~5000K to ~4500K and resulting in an increased DE00 as a result of the added chroma when compared against a standard D50; nearly doubled in best case scenario and nearly tripled in worst case scenario.
The use of polarization while trying to keep the digital color reproduction accuracy at its finest is very challenging due to how polarization is interacting and affecting the light spectrum itself and due to the quality of the used polarization materials. Our study on RGB imaging and color reproduction’s fidelity with and without polarization shows that a cross circular polarization (on a camera lens and light source) will have a major impact on how a linear grayscale, whether it has a semi-glossy or matt finishing, would be reproduced in contrast to no polarization at all. A major loss in deep black shades in the case of a semi-glossy grayscale is unmistakable. In addition to a noticeable shift in both lightness and Chroma components regardless of the grayscale’s finishing but depending rather on the used color target for correction. DE00 could not paint the full picture about color fidelity despite its low conformant reported values. Whereas, a closer visual inspection of the color components separately (lightness and Chroma) reveals color reproduction problems caused by polarization.
Evaluating the utility of polarimetric imaging for material identification, as compared to conventional irradiance imaging, motivates this work. Images of diffuse objects captured with a wide field of view Mueller matrix polarimeter are used to demonstrate a classification and measurement optimization method. This imaging study is designed to test polarimetric utility in discriminating white fabric from white wood. The material color is constrained to be similar so that classification from only total radiance imaging is difficult, i.e., metamerism. A statistical divergence between two distributions of measured intensity is used to optimize the Polarization State Generator (PSG) and the Polarization State Analyzer (PSA) given two classes of Mueller matrices. The classification performance as a function of number of polarimetric measurements is computed. This work demonstrates that two polarimetric measurements of white fabric and white wood offer nearly perfect classification. The utility and design of partial Mueller imaging is supported by this optimization of PSG/PSA states and number of measurements. c 2020 Society for Imaging Science and Technology.